Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!uakari.primate.wisc.edu!indri!xanth!mcnc!kk
From: kk@mcnc.org (Krzysztof Kozminski)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Wide offscreen bitmap won't receive draw commands
Message-ID: <1336@speedy.mcnc.org>
Date: 21 Aug 89 14:17:02 GMT
References: <22321@andante.UUCP> <30755@ucbvax.BERKELEY.EDU> <34168@apple.Apple.COM>
Reply-To: kk@mcnc.org.UUCP (Krzysztof Kozminski)
Organization: Microelectronics Center of NC; RTP, NC
Lines: 31

In article <34168@apple.Apple.COM> keith@Apple.COM (Keith Rollin) writes:
>In article <30755@ucbvax.BERKELEY.EDU> oster@dewey.soe.berkeley.edu.UUCP (David Phillip Oster) writes:
>>In article <22321@andante.UUCP> bwb@andante.UUCP (Bruce Ballard) writes:
>>>What am I missing?

One thing not mentioned by previous posters: be sure to do EraseRect on
your entire off-screen bitmap before you start drawing (lack of this may
account for the garbage you saw after drawing). If I remember correctly,
the code given in TN129 (or is it 126?) has no provisions for cleaning
the off-screen drawing area.

>>Big off-screen grafports should probably do a:
>>	ClipRect(&thePort->portRect);

The above is probably superfluous: the drawing gets clipped to portRect anyway.

>>	RectRgn(thePort->visRgn, &thePort->portRect);
>>before drawing on it.
>
>Dave, I think that Bruce also read the line in Inside Mac, page I-149 that
>says "The visRgn has no effect on images that aren't displayed on the screen."
>I don't know if that warning is correct or not (...)

As far as I can tell, IM is not correct: drawing does get clipped to visRgn.
I have fresh a recollection of creating an off-screen bitmap to produce image
for printing and doing CopyBits to the printer port just to find out that
I was getting 640x480 pixel image ...

KK
-- 
"The party was a masquerade; the guests were all wearing their faces."